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Researchers have found that two of the most important coral species comprising Florida's reef are now functionally extinct after a withering ocean heatwave led to catastrophic losses.

What 'Functional Extinction' Signifies

The almost complete decline of these corals, which once formed the backbone of reefs in Florida and the Caribbean, indicates they can no longer play their once vital role in building and sustaining reef ecosystems that host a variety of marine life.

Ecological extinction is a phase preceding global extinction, a danger that now hangs for many coral species.

Scientists this month alerted that a critical threshold had been reached, meaning corals globally are likely to be eradicated due to global heating, which is raising ocean temperatures to intolerable levels.

Researcher Perspective

"Time is running out," stated Ross Cunning of the new Florida study. "Severe marine heatwaves are becoming more frequent and intense due to global warming, and absent swift, decisive measures to slow ocean warming and enhance coral survival, we face the danger of the extinction of even more corals from reefs in Florida and around the world."

The Recent Study

The recent study, published in the Science journal, analyzed the fate of staghorn and elkhorn coral corals off the Florida coast following a intense marine heatwave in 2023.

This event raised temperatures on Florida's fraying coral reefs to their highest levels in over 150 years.

The two species are complex, reef-building corals and are named because they resemble, in turn, the antlers of stags and elks.

However, scientists who performed diver surveys of more than 52,000 colonies of the species, across 391 sites along Florida's coast, found extensive, often catastrophic, losses.

Geographic Impact

• In the Florida Keys, death rates reached 98% and even one hundred percent, revealing a total eradication of the corals.
• In southeastern Florida, where temperatures have been lower, mortality rates were lower, at about thirty-eight percent.

Past and Current Dangers

The two Acropora species had already endured from many years of regional pressures in Florida, such as poor water quality from pollutants that run off the land, as well as illness.

But the 2023 heatwave has proved lethal for these temperature-sensitive species.

The 2023 heat event caused the ninth occurrence of coral bleaching on the Florida reef – a process whereby corals become heat-stressed and expel the symbiotic algae living in their tissues, causing them to become ghostly white.

If temperatures remain elevated, the corals die off completely.

Worldwide Implications

Worldwide, coral reefs are among the ecosystems most vulnerable to the human-caused climate crisis.

This poses a significant danger to:

• A quarter of all ocean life that relies upon what are effectively the rainforests of the sea.
• Hundreds of millions of people who rely on corals to support fish that they can eat and earn a livelihood from.

Corals also serve as a protective barrier to protect our shorelines from powerful storms, which are themselves being worsened by rising global temperatures.

Conservation Attempts

In a desperate attempt to prevent a decline of endangered corals, scientists have established collections of Acropora in aquariums and ocean-based nurseries.

Attempts have been undertaken to reseed corals on reefs in Florida, too, in an effort to restore some of the ninety percent of coral cover disappeared off the state in the last forty years.

But as global heating continues to intensify, there is little hope of continued existence of these species absent major interventions, scientists caution.

Additional Expert Commentary

"Elkhorn species, especially, are some of the most important wave-dampening coral species in the area," said a study co-author, a ocean scientist at the University of Miami.

"They used to be common on shallow reef tops in the Caribbean, and if we want our reefs to continue protecting our coastlines from flooding during storms, its worth taking exceptional steps to ensure we preserve these corals altogether."